BACKGROUND: Overall survival (OS) has been traditionally used as the primary endpoint in oncology trials, however cross-over to 2nd line agents may result in biases for OS. Recent trials have used progression free survival (PFS) as the primary endpoint. Understanding patient preferences regarding expected PFS vs. avoidance of risk for toxicities in medical decision-making is needed. OBJECTIVES: To estimate RCC patients’ willingness to accept toxicities and medication-related risks to increase PFS. METHODS: US residents aged 18 years and over with RCC completed a web-enabled, choice-format conjoint survey that presented a series of 12 trade-off questions, each including a pair of hypothetical RCC medication profiles. Each profile was defined by efficacy (PFS), tolerability effects (fatigue, diarrhea, hand-foot syndrome, mouth sores), and medication-related risks (liver failure, blood clot). OS was held constant at 32 months. Trade-off questions were based on predetermined experimental design with known statistical properties. Random-parameters logit model was used to estimate a preference weight for each attribute level.  Preference weights were used to calculate maximum levels of risks patients were willing to accept for increases in PFS. RESULTS: A total of 138 US subjects completed the survey. PFS was the most important attribute to patients over the range of levels included in the survey, while remaining attributes were ranked in order of importance as: fatigue, diarrhea, liver failure, hand-foot syndrome, blood clot, mouth sores. Increasing PFS by 10 months was as important as avoiding severe fatigue and 2-times as important as avoiding severe mouth sores. Patients were willing to accept blood-clot risks up to 5.5% (95% CI: 3.6% - 8.6%) and liver-failure risks up to 3.6% (95% CI: 2.6% - 4.8%) to increase PFS by 10 months. CONCLUSIONS: PFS is a clinical outcome that is important to RCC patients. Patients were willing to accept higher treatment-related risks to increase PFS.